1. Field of the Invention
The present invention relates to a liquid-confined vibration isolator for use as an engine mount of a vehicle or a like device.
2. Description of the Related Art
A conventionally known liquid-confined vibration isolator is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. H07-89356. The liquid-confined vibration isolator includes an upper metallic mounting member and a metallic body member, which are disposed away from each other, and a rubber elastic-body for elastically connecting the upper metallic mounting member and the metallic body member. The vibration isolator further includes a stopper portion extending outward from the metallic body member, and a stabilizer extending from the upper metallic mounting member toward the stopper portion while a predetermined clearance is maintained therebetween. A lower metallic mounting member is fixedly crimped to a lower end portion of the metallic body member. The stopper portion is formed such that a flange portion of the metallic body member and a metallic stopper member are united while being superposed, by means of bending or like working. In the vibration isolator, contact between the stopper portion and the stabilizer prevents deformation of the rubber elastic-body in excess of a predetermined limit. Similarly configured liquid-confined vibration isolators are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 2000-297837 and 2001-116080.
The above-mentioned liquid-confined vibration isolator must use the discrete stabilizer in order to prevent excessive deformation of the rubber elastic-body, thus increasing its weight and rendering its assembly work complicated. Also, the lower metallic mounting member must be fixedly crimped to the lower end portion of the metallic body member, thereby rendering its mounting work complicated.
An object of the present invention is to solve the above-mentioned problems and to provide a liquid-confined vibration isolator capable of imparting sufficient strength to a stopper portion by a simple structure, without an accompanying increase in weight, and facilitating assembly work.
To achieve the above object, the present invention provides a liquid-confined vibration isolator comprising a first metallic mounting member; a cylindrical metallic body member disposed away from the first metallic mounting member in the vibration input direction, the metallic body member having a first protrusion protruding radially outward from one axial end thereof facing the first metallic mounting member; an elastic body portion elastically connecting the first metallic mounting member and the metallic body member and plugging the axial end of the metallic body member; a seal portion plugging an axially opposite end of the metallic body member to thereby define a liquid chamber in cooperation with the first metallic mounting member, the metallic body member and the elastic body portion; a cylindrical second metallic mounting member fixedly press-fitted onto the metallic body member and having a second protrusion protruding radially outward from one axial end thereof, the second protrusion and the first protrusion being superposed to thereby form a stopper portion; and a stopper-covering elastic-body portion covering the first and second protrusions of the stopper portion.
In the above-described liquid-confined vibration isolator, the stopper portion is formed through superposition of the first protrusion of the metallic body member and the second protrusion of the second metallic mounting member, thereby obviating use of a discrete stopper member. Therefore, the present invention can simplify the structure of the stopper portion and thus can form the stopper portion at low cost. Also, the structure of superposing the first protrusion of the metallic body member and the second protrusion of the second metallic mounting member imparts sufficient strength to the stopper portion, thereby allowing a weight reduction for the metallic body member and the second metallic mounting member and thus reducing the total weight of the vibration isolator. Further, in assembly of the vibration isolator of the present invention, the second metallic mounting member is fixedly press-fitted onto the metallic body member, thereby obviating complicated press working such as bending and crimping. As a result, the assembly of the vibration isolator is simplified, thereby reducing manufacturing cost. Also, the stopper portion is formed through superposition of the first protrusion of the metallic body member and the second protrusion of the second metallic mounting member, which are covered and held together by the stopper-covering elastic-body portion, thereby reliably preventing detachment of the second metallic mounting member from the metallic body member, which could otherwise result from vibration input to the vibration isolator and other factors.
Preferably, the stopper-covering elastic-body portion is formed integrally with the elastic body portion, thereby eliminating a step of forming a discrete stopper-covering elastic-body portion and thus reducing the manufacturing cost of the vibration isolator.
Preferably, the first and second protrusions constituting the stopper portion are disposed at the same circumferential position, and the stopper-covering elastic-body portion covers opposite side faces of the first and second protrusions in addition to opposite planar faces and protruding end faces of the first and second protrusions. Thus, when vibration is imposed on the vibration isolator in the direction connecting the opposite side faces of the stopper portion, the stopper-covering elastic-body portion that covers the opposite side faces prevents direct contact of the metallic stopper portion against an opponent member. By virtue of opponent members being disposed on opposite sides of the stopper portion with an appropriate distance away from the corresponding opposite side faces of the stopper portion, when excess vibration is imposed on the vibration isolator in the direction connecting the opposite side faces of the stopper portion, the stopper portion covered with the stopper-covering elastic-body portion comes into contact with the opponent members, thereby suppressing the intensity of vibration imposed on the vibration isolator within an appropriate range and thus ensuring the reliability of the vibration isolator.
Preferably, the stopper-covering elastic-body portion is a discrete member formed separately from the elastic body portion and is fixedly fitted onto the stopper portion formed through superposition of the first and second protrusions. Although an additional step is involved to form the discrete stopper-covering elastic-body portion separately from the elastic body portion, when the first protrusion and the second protrusion are to be superposed in the course of press-fitting the second metallic mounting member onto the metallic body member, a step of bending the covering elastic-body portion becomes unnecessary. Thus, press-fitting the second metallic mounting member onto the metallic body member can be simplified, and the stopper-covering elastic-body member can be fixedly fitted onto the stopper portion in an easy and reliable manner.
The present invention also provides a liquid-confined vibration isolator comprising a first metallic mounting member; a cylindrical metallic body member disposed away from the first metallic mounting member in the vibration input direction, the metallic body member having a protrusion protruding radially outward from one axial end thereof facing the first metallic mounting member; a reinforcement member extending radially outward along a back surface of the protrusion and being fixedly disposed while being superimposed on the back surface of the protrusion to thereby form a stopper portion in cooperation with the protrusion; an elastic body portion elastically connecting the first metallic mounting member and the metallic body member, plugging the axial end of the metallic body member, and covering the protrusion and the reinforcement member of the stopper portion; a seal portion plugging an axially opposite end of the metallic body member to thereby define a liquid chamber in cooperation with the first metallic mounting member, the metallic body member and the elastic body portion; and a cylindrical second metallic mounting member fixedly press-fitted onto the metallic body member and having a cutout formed therein so as to avoid interference with the reinforcement member.
In the above-described liquid-confined vibration isolator, the stopper portion is formed through superposition of the protrusion of the metallic body member and the reinforcement member, thereby obviating use of a discrete stopper member. Therefore, the present invention can simplify the structure of the stopper portion and thus can form the stopper portion at low cost. Also, the structure of superposing the protrusion of the metallic body member and the reinforcement member to form the unitary stopper portion imparts sufficient strength to the stopper portion, thereby allowing a weight reduction for the metallic body member and the reinforcement member and thus reducing the total weight of the vibration isolator. Further, in assembly of the vibration isolator of the present invention, the second metallic mounting member is fixedly press-fitted onto the metallic body member, thereby obviating complicated press working such as bending and crimping. As a result, the present invention allows simplification of the assembly of the vibration isolator, thereby reducing manufacturing cost.